Illana, A. et al, & Perez-Vidal, R. M. (2024). Octupole correlations in the N = Z+2=56 110Xe nucleus. Phys. Lett. B, 848, 138371–7pp.
Abstract: This letter reports on the first observation of an octupole band in the neutron-deficient (N = Z + 2) nucleus Xe-110. The Xe-110 nuclei were produced via the Fe-54(Ni-58,2n) fusion-evaporation reaction. The emitted gamma rays were detected using the jurogam 3 gamma-ray spectrometer, while the fusion-evaporation residues were separated with the MARA separator at the Accelerator Laboratory of the University of Jyv & auml;skyl & auml;, Finland. The experimental observation of the low-lying 3(-) and 5(-) states and inter-band E1 transitions between the ground-state band and the octupole band proves the importance of octupole correlations in this region. These new experimental data combined with theoretical calculations using the symmetry-conserving configuration-mixing method, based on a Gogny energy density functional, have been interpreted as an evidence of enhanced octupole correlations in neutron-deficient xenon isotopes.
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n_TOF Collaboration(Gawlik, A. et al), Domingo-Pardo, C., Tain, J. L., & Tarifeño-Saldivia, A. (2021). Radiative Neutron Capture Cross-Section Measurement of Ge Isotopes at n_TOF CERN Facility and Its Importance for Stellar Nucleosynthesis. Acta Phys. Pol. A, 139(4), 383–388.
Abstract: This manuscript summarizes the results of radiative neutron capture cross-section measurements on two stable germanium isotopes, Ge-70 and Ge-73. Experiments were performed at the n_TOF facility at CERN via the time-of-flight technique, over a wide neutron energy range, for all stable germanium isotopes (70,72,73,74, and 76). Results for Ge-70 [Phys. Rev. C 100, 045804 (2019)] and Ge-73 [Phys. Lett. B 790, 458 (2019)] are already published. In the field of nuclear structure, such measurements allow to study excited levels close to the neutron binding energy and to obtain information on nuclear properties. In stellar nucleosynthesis research, neutron induced reactions on germanium are of importance for nucleosynthesis in the weak component of the slow neutron capture processes.
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n_TOF Collaboration(Lederer-Woods, C. et al), Domingo-Pardo, C., Tain, J. L., & Tarifeño-Saldivia, A. (2019). Measurement of Ge-73(n, gamma) cross sections and implications for stellar nucleosynthesis. Phys. Lett. B, 790, 458–465.
Abstract: Ge-73(n, gamma) cross sections were measured at the neutron time-of-flight facility n_TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV. Results indicate that the stellar cross section at kT = 30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of Ge-73 produced in stars, which would explain the low isotopic abundance of Ge-73 in the solar system.
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Guerrero, C., Tessler, M., Paul, M., Lerendegui-Marco, J., Heinitz, S., Maugeri, E. A., et al. (2019). The s-process in the Nd-Pm-Sm region: Neutron activation of Pm-147. Phys. Lett. B, 797, 134809–6pp.
Abstract: The Nd-Pm-Sm branching is of interest for the study of the s-process, related to the production of heavy elements in stars. As Sm-148 and Sm-150 are s-only isotopes, the understanding of the branching allows constraining the s-process neutron density. In this context the key physics input needed is the cross section of the three unstable nuclides in the region: Nd-147 (10.98 d half-life), Pm-147 (2.62 yr) and Pm-148 (5.37 d). This paper reports on the activation measurement of Pm-147, the longest-lived of the three nuclides. The cross section measurement has been carried out by activation at the SARAF LiLiT facility using a 56(2) μg target. Compared to the single previous measurement of Pm-147, the measurement presented herein benefits from a target 2000 times more massive. The resulting Maxwellian Averaged Cross Section (MACS) to the ground and metastable states in Pm-148 are 469(50) mb and 357(27) mb. These values are 41% higher (to the ground state) and 15% lower (to the metastable state) than the values reported so far, leading however to a total cross section of 826(107) mb consistent within uncertainties with the previous result and hence leaving unchanged the previous calculation of the s-process neutron density.
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Pasqualato, G. et al, Gadea, A., & Jurado, M. (2023). An alternative viewpoint on the nuclear structure towards 100Sn: Lifetime measurements in 105Sn. Phys. Lett. B, 845, 138148–7pp.
Abstract: This work aims at presenting an alternative approach to the long standing problem of the B(E2) values in Sn isotopes in the vicinity of the N=Z double-magic nucleus Sn-100, until now predominantly measured with relativistic and intermediate-energy Coulomb excitation reactions. The direct measurement of the lifetime of low-lying excited states in odd-even Sn isotopes provides a new and precise guidance for the theoretical description of the nuclear structure in this region. Lifetime measurements have been performed in Sn-105 for the first time with the coincidence Recoil Distance Doppler Shift technique. The lifetime results for the 7/2(1)(+) first excited state and the 11/2(1)(+) state, 2(+)(Sn-104) circle times nu 1g(7/2) multiplet member, are discussed in comparison with state-of-the-art shell model and mean field calculations, highlighting the crucial contribution of proton excitation across the core of Sn-100. The reduced transition probability B(E2) of the 11/2(1)(+) core-coupled state points out an enhanced staggering with respect to the B(E2; 2(1)(+) -> 0(1)(+)) in the even-mass Sn-104 and Sn-106 isotopes.
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